A long time ago, there lived a jorougumo named Hatsune who gathered enough celestial energy that she was able to take a human form.

One day, a mysterious monk came to Hatsune's nest and nearly annihilated her for taking a villager's life. Severely wounded, Hatsune went into hiding. To heal her wounds, she decided to make Yaesaka High School her new nest and absorb energy from the students attending there. Hatsune absorbs energy by eating the flesh of (mostly male) students or through having sexual intercourse with them (preferably with females).

Hatsune Hirasaka: A jorougumo who has lived for many hundreds of years. Although for the last hundred or so she has stayed hidden in a forest, due to being seriously injured when fighting with her old enemy Shirogane, who appeared in the world of humans. By raping men and women, she can obtain life energy and conserve power.

Kanako Miyama: A first-year student at Yaesaka High School and a daughter of a rich man. She became the victim of delinquent students, and was gang-raped in the back of a gymnastics building on the night when Hatsune first appeared. However, Hatsune saved her.

Rin Yagami: A third-year student at Yaesaka, and a miko at Yagami Shrine. She is short and does not look like an upperclassman at all. Has a relation with the silver-haired monk.

Sachiho Takano: A second-year student at Yaesaka. Sickly by nature, with an introverted personality. Takahiro's childhood friend, the two are said to be lovers.

Tsugumi Watanabe: A first-year student at Yaesaka, and Takahiro's younger sister. Belongs to a swimming club, in the same class as Kanako, and an active and spirited girl. But slightly pitiful for being a target of both Hatsune and Iguchi. She is the most popular girl among the staff.

Takahiro Watanabe: President of Yaesaka's student council, a second-year student who is also captain of the kendo club. Sachiho's childhood friend. Owns a sword passed down from generation to generation, for self-defense. Distrustful of Hatsune.

Kazahisa Katsuragi: A second-year student who transferred from another school in Osaka to Yaesaka High. Possessing a bright and spirited personality, one wonders why he likes Kanako, whose character is the exact opposite of his.

Miyuki Hotta: A second-year student at Yaesaka and manager of the kendo club. Since she is charmed by Takahiro, she and Sachiho are connected.

Shirogane: Hatsune's old enemy, who has been crossing over and fighting her for a very long time. He was injured in the previous battle just like Hatsune, and has been conserving power. Although he has a form of a priest, he is not actually one.

Gousuke Iguchi: Gymnastics teacher at Yaesaka and the advisor of the swimming club. Has been stalking Tsugumi.

Keita Ayukawa: A first-year student at Yaesaka, and works as assistant treasurer on the student council. An easily amused person, just like Tsugumi.

↑Written in Japanese as Atlach=Nacha. The = included in the Japanese title causes it to be read in the Western order: given name first, surname last. Normally in Japanese, the surname would come first. Thus, the title is not Atlach Equals Nacha, but simply Atlach-Nacha.